System for separating and classifying solids



W. C. SMITH March 24, 1964 SYSTEM FOR SEPARATING AND CLASSIFYING SOLIDSFiled Oct. 11, 1960 on m- INVENTOR WILLIAM C.SM|TH Mr ATTORNEYS UnitedStates Patent 3,126,337 SYSTEM FGR SEPARATTNG AND CLASSIFYING SOLIDSWilliam C. Smith, Moline, lll., assignor to Ametek, Inc., a corporationof Delaware Filed Oct. 11, 1950, Ser. No. 61,935 1 Claim. (Cl. 233-4)This invention relates to apparatus for conditioning drilling mud or thelike and particularly to a control system therefor.

Drilling mud or fluid is commonly employed in rotary drillingoperations, the mud having a number of functions to perform as is knownin the art. These functions include lubrication of the rotary drill bit,removal of cuttings, overcoming formation pressures in the hole beingdrilled and depositing an impermeable wall cake. With the great increasein depth of wells and the problems of bottom hole temperature andpressure, drilling mud plays a large part in successful completion of awell, the

cost of the mud being very high. Mud must be circulated in the system inthe proper volume and must have the correct viscosity and weight toaccomplish the aforementioned functions etficiently, and the amount ofdrilled solids in the mud must be properly regulated. Chemical treatmentfor control of the solids or addition of water has not beensatisfactory. When clays are mixed with water, hydration results and anincrease in viscosity occurs. Merely removing clay to reduce viscosityis insuflicient because then it becomes necessary toadd Weightingmaterials for particular drilling operations. Barium sulphate or bariteis commonly used as a weighting material and in some areas one of theprincipal considerations in treatment of mud is that of saving bariumsulphate.

The principal object of this invention is to provide a separating andclarifying system in which a constant ratio of water and material to betreated is maintained substantially constant while the density of theeffluent therefrom is maintained substantially constant.

Another object of this invention is to provide such a system that isautomatically controlled.

Still another object of this invention is to provide such a system inwhich a measure of the torque required to drive the beach of a clarifiercombines with a measure of the efiiuent density to control the feed ofthe material to be treated to the clarifier.

Still another object of the invention is to provide such a system inwhich the ratio of material to be treated and Water entering theclarifier is maintained at a predetermined value by signals measuringthe flow of mud and water to the clarifier.

A conventional solids-liquid separator or classifier of the centrifugalor decanting type may include a horizontally disposed, conical-shapedouter bowl or beach within which a conical-shaped screw conveyor may belocated. The conical-shaped beach may be driven at a desired speed andthe conveyor may be connected to the beach through a suitabledifferential or variable drive arrangement. The beach may be driven byone prime mover, while the input shaft of the diflterential gear may bedriven by a hydraulic pump and motor system that is powered by aseparate prime mover. The hydraulic system being a constant torquedevice, the pressure within said system is proportional to the torque orload on the conveyor.

In one aspect of the invention, the effluent leaving the classifier maybe subjected to a density measuring device which may produce a signalthat may be fed to a pneumatic controller along with a measure of thepressure within the hydraulic pump and motor system that drives theconveyor. The output from the controller may be employed to vary thedisplacement of a hydraulic pump and motor system that operates a pumpthat feeds the material to be treated to the clarifier or separator.

In still another aspect of the invention, water or other liquid may befed to the clarifier and mixed with the material to be treated prior tothe admixture entering the clarifier. A predetermined substantiallyconstant ratio of water and material to be treated may be fed to theseparator by measuring the flow of water and the flow of liquid in thehydraulic system that drives the pump feeding the material to be treatedto the separator. These two measurements may be combined within a ratiocontroller for operating a valve that controls the flow of water to theseparator.

The above, other objects and novel features of the system and controlwill become apparent from the following specification and accompanyingdrawing which is merely exemplary.

In the drawing:

The figure is a schematic showing of apparatus to which the principlesof the invention have been applied.

The invention will be described in conjunction with a conventionalhorizontal solids-liquid rotary separator or classifier.

Referring to the drawing, the separator or classifier 10 can be mountedon a suitable base 11, the outer bowl or beach 12 being carried bybearings 13, 13, said beach being driven by a suitable motor 14 throughbelt 15 and pulley 16. A conveyor 10' Within beach 12 can be driven by ashaft 23, the speed thereof and the speed relative to beach 12 beingcontrolled by a suitable dilferential drive arrangement 19, which inturn is operated by a fluid motor system including a variable deliveryfluid pump 21 driven by a motor 22, and a constant displacement fluidmotor Ztl. The fluid motor drives the input shaft 23 of the differentialunit 19, variation of pump delivery, varying the fluid motor speed, andthus controlling the dilferential speed between the beach 12 and theconveyor.

Since the fluid drive will have constant torque characteristics, thetorque of the drive will be that required for conveying solids along thebeach and will be directly pro portional to the pressure in the fluidsystem. This pressure is connected through line 24 to a pneumaticcontroller 25 for a purpose to be described later. Pneumatic controller25, for example, can be similar to that shown in Patent No. 2,770,247,although other types of con troller can be used.

Mud to be treated may be supplied from a tank 26 to a pump 27, theoutlet 28 therefrom being connected to a T-fitting 29 leading to theseparator 10. The pump 27 may be driven by a hydraulic constantdisplacement motor 39 that is driven by a variable displacementhydraulic pump 31 which latter may be driven by a suitable prime mover(not shown). Pump 31 and motor 3t) are connected together by hydrauliclines 32 and 33. L1 the return line 33, an orifice 34 may be located formeasuring the flow of oil through the pump 31 and motor 30. Pressurelines 35 and 36 from the orifice 34 may lead to a diflerential pressurecell 37, such, for example, as those manufactured by The Foxboro Companyof Foxboro, Massachusetts, and known as their Model 13A. The outputsignal 33 from the cell 37 may lead to a ratio controller 39 for apurpose presently to be described.

Water is adapted to be introduced into the separator 10 from a supplyline 40 that includes a control valve 41 therein which may bepneumatically operated. The water may flow through a line 42 leading tothe T-fitting 29 which latter is spaced sufliciently from the separatorto ensure proper mixing of the water and mud before it enters separator10.

An orifice device 43 may be located in line 42 for measuring the waterflow therethrough, and it may be connected through lines 44 and 4-5 toanother differential pressure cell 46, the output signal 47 therefromleading to the ratio controller 39. The ratio controller 39 may be ofthe type manufactured by The Foxboro Company and known as their ModelM/40. It may be preset to maintain a predetermined fixed ratio of mud towater entering the separator 10 and its signal 48 may control theoperation of the pneumatic valve 41 to maintain such ratio constant.

While a predetermined ratio of mud to water may be maintained constantin passing into the separator 10, the efiluent leaving the separator mayvary in density depending upon the duration of time the mixture remainsin the separator. In order to maintain the density of the efiluentsubstantially constant, it is caused to pass out from the separator 10through a line 49 leading to a U-tube arrangement 50 similar to amanometer.

In the line 49, forming one leg of the U-tube arrangement 50, may belocated in spaced relation two differential pressure cells 51 and 52 ofa particular design. They may be of the type manufactured by The FoxboroCompany and known as their Model 13A. They present to the efiluent inline 49 diaphragms 53 and 54. The signals 55 and 56 from the cells 51and 52 are fed to a subtraction relay 57, the output signal 58 fromwhich leads to the load controller 25.

As previously explained, load controller 25 also receives a signal fromline 24, and the output signal 59 therefrom controls the variabledisplacement pump 31 to control the amount of mud being fed by the mudpump 27 to the separator 10. At the same time, the ratio of mud to Wateris maintained substantially constant to thereby produce an effluent ofsubstantially constant density.

Although the various features of the new and improved separating systemand control therefor have been described in detail to fully disclose oneembodiment of the invention, it will be evident that changes may be madein such details and certain features may be used without others withoutdeparting from the principles of the invention.

What is claimed is:

A system for separating and classifying solids, comprising incombination a separator including a rotatable beach and a rotatableconveyor therein; means for driving said beach; a hydraulic pump andmotor system for driving said conveyor in a predetermined relationrelative to said beach; a pump for feeding material to be treated tosaid separator; a hydraulic variable displacement pump and motor systemfor driving said feeding material pump; means for measuring the densityof the efiluent discharging from said separator; a controller responsiveto the pressure of liquid in said conveyor driving system and thedensity of said efiluent for varying the displacement of said variabledisplacement pump and thereby the amount of separation; and adjustablemeans responsive to the flow of liquid in said variable displacementpump and motor system and the flow of liquid to said separator formaintaining substantially constant a predetermined ratio of liquid tomaterial to be treated being fed to said separator.

References Cited in the file of this patent UNITED STATES PATENTS1,901,032 Kallam Mar. 14, 1933 2,532,792 Svensjo Dec. 5, 1950 2,895,669Bobo July 21, 1959 2,955,753 OConor et al. Oct. 11, 1960 2,961,154Bergey Nov. 22, 1960

